1 files changed, 113 insertions, 0 deletions
diff --git a/json4cpp/tests/src/unit-hash.cpp b/json4cpp/tests/src/unit-hash.cpp
new file mode 100644
index 0000000000..c161efa6e9
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+++ b/json4cpp/tests/src/unit-hash.cpp
@@ -0,0 +1,113 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#include "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
+
+#include <set>
+
+TEST_CASE("hash<nlohmann::json>")
+{
+    // Collect hashes for different JSON values and make sure that they are distinct
+    // We cannot compare against fixed values, because the implementation of
+    // std::hash may differ between compilers.
+
+    std::set<std::size_t> hashes;
+
+    // null
+    hashes.insert(std::hash<json> {}(json(nullptr)));
+
+    // boolean
+    hashes.insert(std::hash<json> {}(json(true)));
+    hashes.insert(std::hash<json> {}(json(false)));
+
+    // string
+    hashes.insert(std::hash<json> {}(json("")));
+    hashes.insert(std::hash<json> {}(json("foo")));
+
+    // number
+    hashes.insert(std::hash<json> {}(json(0)));
+    hashes.insert(std::hash<json> {}(json(static_cast<unsigned>(0))));
+
+    hashes.insert(std::hash<json> {}(json(-1)));
+    hashes.insert(std::hash<json> {}(json(0.0)));
+    hashes.insert(std::hash<json> {}(json(42.23)));
+
+    // array
+    hashes.insert(std::hash<json> {}(json::array()));
+    hashes.insert(std::hash<json> {}(json::array({1, 2, 3})));
+
+    // object
+    hashes.insert(std::hash<json> {}(json::object()));
+    hashes.insert(std::hash<json> {}(json::object({{"foo", "bar"}})));
+
+    // binary
+    hashes.insert(std::hash<json> {}(json::binary({})));
+    hashes.insert(std::hash<json> {}(json::binary({}, 0)));
+    hashes.insert(std::hash<json> {}(json::binary({}, 42)));
+    hashes.insert(std::hash<json> {}(json::binary({1, 2, 3})));
+    hashes.insert(std::hash<json> {}(json::binary({1, 2, 3}, 0)));
+    hashes.insert(std::hash<json> {}(json::binary({1, 2, 3}, 42)));
+
+    // discarded
+    hashes.insert(std::hash<json> {}(json(json::value_t::discarded)));
+
+    CHECK(hashes.size() == 21);
+}
+
+TEST_CASE("hash<nlohmann::ordered_json>")
+{
+    // Collect hashes for different JSON values and make sure that they are distinct
+    // We cannot compare against fixed values, because the implementation of
+    // std::hash may differ between compilers.
+
+    std::set<std::size_t> hashes;
+
+    // null
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(nullptr)));
+
+    // boolean
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(true)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(false)));
+
+    // string
+    hashes.insert(std::hash<ordered_json> {}(ordered_json("")));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json("foo")));
+
+    // number
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(static_cast<unsigned>(0))));
+
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(-1)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(0.0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(42.23)));
+
+    // array
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::array()));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::array({1, 2, 3})));
+
+    // object
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::object()));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::object({{"foo", "bar"}})));
+
+    // binary
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({})));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({}, 0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({}, 42)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3})));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3}, 0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3}, 42)));
+
+    // discarded
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(ordered_json::value_t::discarded)));
+
+    CHECK(hashes.size() == 21);
+}